Pipe usable particularly for transporting fluids and allowing the permeability to the fluids transported to be limited

ABSTRACT

Disclosed is a rigid or flexible conduit usable particularly for transporting fluids and enabling to limit the permeability to transported fluids. According to the invention, the conduit comprises at least an inner flexible sheath (1) made of thermoplastic, elastic, or rubber material and an outer sheath (10) comprising a metal layer (3) and arranged around said inner sheath (1). Said metal layer comprises at least a layer of flat metal band (3) which is spirally wound with a winding angle α higher than 50° and lower than 90° with respect to the axes of the conduit. For rigid conduits, said metal layer (3) is adhered to said inner flexible sheath (1) on the major part of the width of the band (3). For flexible conduits, the turns present superposition areas so as to provide for a complete covering of said inner sheath (1), the superposition areas (30) of the band turns on one hand and the areas comprised between said superposition areas on the other hand, having each a width at least equal to amplitude of the deformation imposed to the outer sheath by the maximum bending or traction of the conduit. Application particularly to the transportion of corrosive fluids under pressure, to the oil industry at the drilling site or the production.

The present invention relates to a pipe usable in particular fortransporting fluids and allowing the permeability to the fluidstransported, for example corrosive fluids, to be limited.

The invention relates in particular to the field of transporting liquidor gaseous fluids, particularly hydrocarbons, in pipes likely to be usedat high pressure and high temperatures for long periods of time.

The application of the invention to the production of flexible pipes andrigid reinforced-resin pipes will be considered in particular below.

Here, flexible tubes or pipes are understood to be pipes havingsufficient flexibility to accept (without deterioration) a radius ofcurvature R less than or equal to a×d, wherein d is the diameter of thetube measured in the same unit as R and a is a numerical coefficientwhose value does not exceed a few units, 4 to 5 for example.

A flexible pipe designed to operate under high pressure is composed forexample of the following elements:

a folded metal strip designed to prevent the pipe from being crushed bythe pressure differential between the inside and the outside;

a flexible inner sheath made of plastic or elastomer, making the pipelargely impermeable on the inside;

at least one reinforcing layer to withstand tensile and/or internalpressure forces, and

a second flexible plastic or elastomer sheath to ensure externalimpermeability of the pipe.

A rigid pipe designed to operate under high pressure is composed forexample of the following elements:

a soft, inner, highly flexible sheath

an outer sheath formed by winding fibers pre-impregnated with athermosetting resin.

The problems involved in transportation of liquid or gaseous fluids athigh temperatures and pressures in these types of pipes are linked tothe permeability of the products used.

For flexible pipes, these problems are (1) permeability of the materialof which the inner sealing sheath is composed, whereby this permeabilityincreases very substantially with temperature and pressure, and (2)accumulation of gas between the inner and outer sheaths due to the factthat the permeability of the outer sheath may be far less than that ofthe inner sheath.

Particularly in the case of transporting liquid or gaseous hydrocarbonslikely to contain corrosive agents such as H₂ S, CO₂, etc., thisaccumulation may cause accelerated corrosion of the metalreinforcements.

In addition, the pressure prevailing between the two sealing layers maybecome greater than the external pressure applied to the flexible pipeand cause the outer sheath to shatter.

Moreover, these permeability phenomena result in varying degrees of lossof transported fluid.

For rigid pipes, these problems are due to the limited flexibility ofthe pipes which causes microcracking under mechanical stress, which canlead to "sweating" of the fluid.

It is known that the use of continuous corrugated metal in a flexiblepipe instead of the plastic inner sheath avoids the drawbacks inherentin plastic sheaths, but this solution has the drawback of greatsensitivity to corrosion, the corrugated metal being in direct contactwith the fluid. Moreover, the geometry of the metal can disturb the flowof the fluids or passage of any special tools (measuring or cleaningtools for example) through the pipe.

European patent application EP-A-0.111.169 relates to a multi-layergastight tube. It has in particular a metal envelope integral with theouter periphery of a plastic sheath and with the inner periphery of anouter tube. The integral assembly is spiral-wound edge to edge, eitherhot such as to form a seal with the plastic sheath which has beensoftened, or by means of a cold-setting or hot-setting cement. Thisedge-to-edge winding technique of layers which are integral with eachother can only be applied to rigid tubes and not to flexible tubes whichwould then lose all their flexibility.

The prior art of pipe-making techniques is illustrated for example bypatents FR-A-2.467.347 or EP-A-0.068.128.

When applied to flexible tubes, the present invention allows thepermeability of the flexible sheaths to be limited without altering theinternal geometry of the tube and without reducing the flexibility ofthe pipe. It relates to a pipe usable in particular for transportingfluid, possibly under pressure, allowing the permeability to the fluidstransported to be limited, comprising an inner flexible sheath made of athermoplastic material or elastomer, and an outer sheath having a metallayer and being disposed around said inner sheath, characterized by saidmetal layer having at least one flat metal band layer wound spirally ata winding angle α greater than 50° and less than 90° to the pipe axis,the turns of this band having overlap zones such as to ensure fullwrapping of said inner sheath, the overlap zones of the band and thezones between said overlap zones each having a width at least equal tothe degree of deformation imposed on the outer sheath by the maximumstretching or bending of the pipe.

One of the essential advantages of the wrap so provided according to theinvention is contact of the metal layers under the effect of pressure ofthe fluids on the inner sheath, which reinforces the impermeability ofthe flexible pipe while keeping its flexibility intact because playexists between the turns.

The metal layer may have a metal band layer cemented to said innersheath over a part of the width of this layer in contact with said innersheath, so that there is free play between the turns of the metal band,conferring great freedom of movement on the turns when the flexible pipeis test-coiled or uncoiled.

It may also be advantageous, according to another embodiment, for themetal layer to have a metal band layer cemented to an outer envelopeover part of the width of said layer in contact with said outerenvelope, with the turns of the metal band being able to have free playwith respect to each other.

The cementing as described may make it possible to avoid the changing ofthe winding pitch that may result from deformation of the pipe when itis handled for storage and/or service. Also, cementing can be performedcontinuously or discontinuously, but better results have been obtainedwhen cementing was continuous over a part of the band in contact withone or the other of the flexible sheaths.

Advantageously, the band can be cemented to the edge in contact withsaid inner sheath or with the outer envelope, to avoid relativemovements of this edge in contact with the sheath or envelope anddecrease the risk of chipping of the sheath or envelope by this edge incontact with fluid on the inside or outside.

The metal layer according to the invention can be cemented with acold-setting or hot-setting cement or hot-melting glue depending on thesituation or the type of material. An adhesion primer may also beapplied to the sheath and/or band.

According to another embodiment, the pipe may have at least twosuperimposed layers of metal band, the layer of band in contact with theinner sheath being cemented to the sheath over part of the width of themetal band and the layer in contact with the outer sheath being cementedthereto over part of the width of the metal band.

The objective of the present invention applied to rigid pipes isachieved by winding, between the flexible inner sheath and the outersheath formed by winding fibers pre-impregnated with a thermosettingresin, at least one layer of flat metal band which is cemented to theinner sheath over at least the majority of the width of the band.

This band is spirally wound at a winding angle α greater than 50° andless than 90° to the pipe axis, the turns of this band having overlapzones such as to ensure a full wrap of said inner sheath, both theoverlap zones of the turns of the band and the zones between saidoverlap zones each having a width at least equal to the degree ofdeformation imposed on said sheaths by maximum stretching or bending ofthe pipe or by decompression.

The overlap zones are not cemented. However, if it is preferred tocement them to improve their impermeability, a flexible cement of theneoprene type able to accept the deformation imposed will preferably beselected.

Cementing as described may allow a virtually gastight pipe with aconstant cross section to be obtained and prevent changes in the windingpitch that might result from deformations of the pipe when handled forstorage and/or in service.

Both for rigid pipes and for flexible pipes, one may preferably usebands made of amorphous metal strips or amorphous metal alloys asdescribed in French Patents FR-A-2.368.324 and FR-A-2.381.581 due totheir mechanical properties being superior to those of the correspondingcrystalline metals or alloys, in particular their strength and hardnesscharacteristics (up to 370 kg/mm² and 1100 kg/mm² respectively) andtheir high elastic limit. These amorphous metals are usually used fortheir isotropic mechanical strengths and other isotropic physicalproperties such as magnetizability.

Since the fluids to be transported are corrosive, it is preferable touse, especially when the fluids contain hydrosulfuric acid,corrosion-resistant metals such as alloys whose composition includes, inparticular, chromium and/or nickel and/or cobalt and/or molybdenum.

Bands of amorphous metals with a composition which includes, inparticular, iron, chromium, phosphorus, carbon, and possibly nickel,cobalt, or molybdenum, alone or in a mixture, with an atomic percentageof metalloids (P, C, B, etc.) preferably equal to 20% at most, havegiven excellent results in terms of gas-tightness and corrosionresistance. The width of the bands will preferably be equal to at least1 cm and its thickness may vary from 1/100 mm to a few tenths of amillimeter, preferably 5/100 mm to 5/10 mm.

All extrudable thermoplastics or elastomers may be used, with wallthicknesses varying according to each loading case. For example, one mayuse polyamides, polyolefins, or fluorinated polymers (PVDF) as thethermoplastics, and synthetic or natural elastomers.

When the pipe has several sheaths made of a thermoplastic or elastomermaterial such as an outer sheath and an inner sheath, the material ofone sheath may be different from that of the other.

The invention will be better understood with reference to the attachedfigures below showing examples of embodiments:

FIGS. 1, 2, and 3 represent a flexible pipe according to the inventionin lengthwise section,

FIG. 4 shows another embodiment of a flexible pipe according to theinvention in lengthwise section,

FIG. 5 illustrates a preferred embodiment according to the invention inthe case of a high-pressure flexible pipe (the thicknesses of thevarious layers are not shown to the same scale),

FIG. 6 shows a rigid pipe according to the invention in lengthwisesection,

FIG. 7 shows an embodiment of a rigid pipe according to the invention inlengthwise section, and

FIG. 8 illustrates another embodiment of a rigid pipe in lengthwisesection designed for high performance.

In FIGS. 1 to 5, where X-Y is the lengthwise axis of flexible pipe 10, athermoplastic or elastomer inner tube or sheath 1 has been extruded and,according to the invention, a metal band 3 has been wound withsufficient tension to press it against inner sheath 1. The band has beenwound helically at an angle α greater than 50° and less than 90° to theaxis of the pipe, and with overlap zones (30, FIG. 1; 15, 16, and 17,FIG. 4) whose width is at least equal to the degree of deformation(elongation or shortening) imposed on outer sheath 10 during storageand/or in service 10, said sheath possibly having an outer envelope 2and a metal layer 3. This outer sheath 10 has been extruded over themetal layer according to the invention and is applied to its outer part.

According to FIG. 2, this band 3 may be cemented to a part of the widthwhich is in contact 4, namely the edge in contact 5 with said innersheath 1 of the flexible pipe.

According to FIG. 3, the band can be cemented to a part in contact 6,namely to the edge in contact 7 with outer envelope 2 of the flexiblepipe.

FIG. 4 shows another embodiment of the flexible pipe according to theinvention where there has been wound on inner sheath 1 a first layer ofband 3 whose turns 11 and 12 do not overlap and a second layer 3a withturns 13 and 14 covering the former turns and resting against the facingedges 15, 16, and 17 of turns 11 and 12 of layer 3.

The turns of layer 3 are cemented at 5 to inner sheath 1 and the turnsof layer 3a are cemented at 7 to outer envelope 2.

In the preferred embodiment showing a flexible pipe under pressure (FIG.5), an inner sheath 1 4 mm thick made of Rilsan 11 (registeredtrademark) has been extruded over a strip 21 with an outer diameter of100 mm, made of stainless steel.

A thin film of hot-melting glue compatible with Rilsan 11, 3 mm wide, isapplied to the inner sheath at a spiral-winding angle equal to that usedfor winding the band, i.e. about 84° corresponding to a pitch of 24 mm.

Band 3 made of an alloy of amorphous metals, preheated to a temperaturesubstantially higher than the softening point of the glue, isspiral-wound by a known technique at a winding tension of 200 Newtons.

The width of the overlap zones of the adjacent turns represents about20% of the width of these turns, i.e. 6 mm in the example considered,and the band is applied such that only edge 5 of the band is cemented toinner sheath 1.

The amorphous-metal alloy band had the following characteristics, ablein particular to ensure good corrosion resistance:

Composition: Fe₇₂ Cr₈ P₁₃ C₇

Width: 3 cm

Thickness: 20/100 mm.

A flexible outer envelope 2 made of of medium-density polyethylene 2 mmthick was then extruded by a known technique, which covers metal layer 3according to the invention.

Various wraps have been wound over envelope 2:

an S-shaped wrap 22 known as "zeta" and another wrap 23 8 mm thick, bothwound helically at angles of approximately 85° and pressure-resistant,

an armature ply 24 and an armature ply 25 with a coarse pitch, 3 mmthick, with high tensile strength and spiral-wound, one laid right andthe other laid left at an angle of 35° to the axis of the flexible pipe.

finally, a last outer sheath 26.

Under these conditions, a flexible pipe is obtained whose flexibilityremains intact and for which the permeability to methane for example oflayers 1, 2, 3 is reduced by a factor of about 50 to 100 depending onthe utilization conditions, by comparison to a single plastic layer withimpermeability.

It will not be beyond the scope of the invention for example tointerpose a layer of grease such as a layer of grease based on siliconesinsoluble in hydrocarbons and heat-stable, between metal band 3 andsheath 1 and/or envelope 2 on the one hand and/or between the contact oroverlap zones 30 (FIG. 1) and 15, 16, and 17 (FIG. 4) of one turn of theband with the next, on the other hand.

In FIG. 6, where XY represents the axis of the pipe, a flat layer ofmetal band 33 is wound and cemented 35 with a sufficient tension arounda soft, flexible inner sheath 31 made of thermoplastic material orelastomer which is hence supported by the inner face of the band. Thecement has been deposited on the largest surface in contact betweensheath 31 and layer 33.

The band is composed of a winding of turns 34 at an angle α greater than50° and less than 90° to axis XY. Turns 34 of said band 33 have overlapzones 36 in order to accept any deformations upon decompression of thepipe and to ensure total wrapping of inner sheath 31. Overlap zones 36of turns 34 of the band and the zones between the overlap zones bothhave a width at least equal to the degree of deformation (decompression,elongation, or shortening) imposed on sheaths 32 of the pipe.

The impermeability to the gases in the pipe is thus substantiallyimproved. To maintain greater stiffness, the pipe comprising sheath 31and band 33 is surrounded with an outer sheath 32 made of a compositematerial wound at an angle less than 90° to the axis of the pipeaccording to a technique known to the individual skilled in the art.

The composite materials used can be for example glass, carbon, or Kevlar(registered trademark) fibers impregnated with resin, for example epoxy,or composites based on strip steel.

When cold the resin will crosslink and adhere to the metal layer whichwill have been pre-degreased. This type of pipe will be particularlyadvantageous for low and medium performance.

FIG. 7 illustrates another embodiment of a rigid pipe where a firstlayer of band 33 whose turns 41 and 42 do not overlap and a second layer33a whose turns 43 and 44 overlap the previous turns, pressing againstfacing edges 45, 44, 47 of turns 41 and 42 of layer 33, is wound oninner sheath 31.

The turns of layer 33 are cemented at 35 to at least the major part ofthe width in contact with the inner sheath and preferably to the entirewidth of the turns. One winding of an outer sheath 32 made of compositematerial, as above, stiffens the pipe thus formed by adhering to metallayers 33 and 33a.

FIG. 8 shows another embodiment of a high-performance rigid pipe whereinner sheath 31 is cemented 35 and thus supported by metal layer 33 madeof turns 34.

Over this metal layer another thermoplastic or elastomer sheath 31b hasbeen extruded, which sheath presses against and adheres to this layer 33which is hence applied against this soft sheath composed of sheaths 31and 31b. Sheath 31 thus stiffened and substantially gastight is thensurrounded by at least one outer sheath 32 made of a composite materialas described above.

The rigid pipe in its preferred embodiment (FIG. 7), in order towithstand high pressures on the order of 300 bars and high temperatures,has an inner sheath 2 mm thick made of Rilsan 11 (registered trademark),15 cm in diameter. A thin film of hot-melting cement compatible with theRilsan 11, 20 cm thick, is applied to the inner sheath at aspiral-winding angle equal to that used for winding the band, i.e.approximately 84°.

Band 33 made of amorphous metals preheated to a temperaturesubstantially higher than the softening point of the cement isspiral-wound by a known technique at a winding tension of 200 Newtons.

The band of amorphous-metal alloy has the following characteristics,capable in particular of ensuring good corrosion resistance:

Composition: Fe₇₂ Cr₈ P₁₃ C₇

Width: 3 cm

Thickness: 20/100 mm.

The width of the overlap zones of adjacent turns representsapproximately 20% of the width of these turns, or 6 mm in the exampleconsidered, and the band is placed such that the major part of the widthof the turns of band 33 is cemented to inner sheath 31.

After degreasing the upper part of band 33, a plastic Rilsan 11 sheath 1mm thick is extruded by a known techique, levelling layer 33 andfinally, over this sheath 31b, at least one layer of composite fibers asdescribed is wound at winding angles known to the individual skilled inthe art and compatible with the tensile and compressive forces the pipemust withstand.

Under these conditions, a rigid pipe is obtained wherein thepermeability of inner sheath 31 to methane for example is reduced by afactor of about 50 to 100 depending on the utilization conditions.

The invention is not of coursed limited to the embodiments described asexamples.

The pipes according to the invention described above can serve inparticular as means of transporting corrosive fluid hydrocarbons atfairly high pressures and temperatures. These pipes can also be used fordrilling and hydrocarbon production operations which require highdynamic stresses, and metal layer 3, 33 could be used to carryelectrical information underground-to-surface andsurface-to-underground.

The rigid pipes can in particular be used as risers in drilling andhydrocarbon production.

We claim:
 1. A pipe useful for transporting fluids which may be underpressure having limited permeability to fluids transported therein, saidpipe comprising a flexible inner sheath made of a thermoplastic materialor elastomer, an outer sheath comprised of an outer envelope of aflexible polymeric material and a metal layer disposed around said innersheath, said metal layer comprising at least one layer of flexible, thinand flat metal band wound spirally at a winding angle α greater than 50°and less than 90° to an axis of the pipe, turns of said at least onelayer of a flexible, thin and flat metal band having overlapping zonesto ensure total wrapping of said inner sheath, said overlapping zonesbeing provided by consecutive turns of the at least one layer of aflexible, thin and flat metal band, the overlapping zones of the turnsand zones between said overlapping zones both having widths at leastequal to a degree of deformation imposed on the outer sheath by maximumstretching and bending of the pipe; said metal layer being cemented toat least one of the inner sheath and the outer envelope.
 2. A pipeaccording to claim 1, wherein the flexible, thin and flat metal band ismade of an amorphous metal or an amorphous metal alloy.
 3. A pipeaccording to claim 2, wherein the flexible, thin and flat metal band hasa composition containing iron, chromium, phosphorus, carbon and a metalselected from the group consisting of cobalt, molybdenum and nickel,with an atomic percentage of metaloids equal to at most 20%.
 4. A pipeaccording to claim 2, wherein the flexible, thin and flat metal band hasa composition containing iron, chromium, phosphorus and carbon with anatomic percentage of metaloids equal to at most 20%.
 5. A pipe accordingto claim 1, wherein the outer envelope of the sheath is flexible and theflexible, thin and flat metal band is made of an amorphous metal or anamorphous metal alloy.
 6. A pipe according to claim 1, wherein saidmetal layer comprises a layer of a flexible, thin and flat metal bandcemented to said inner sheath, over a part of the width of said metalband in contact with said inner sheath, the turns of the metal bandhaving free play with respect to each other.
 7. A pipe according toclaim 6, wherein the flat metal band is cemented to said inner sheathsubstantially at a level of an edge of the flat metal band in contactwith said inner sheath.
 8. A pipe according to claim 1, wherein saidmetal layer comprises a layer of a flexible, thin and flat metal bandcemented to the outer envelope of a flexible polymeric material over apart of the width of the metal band in contact with said outer envelope,the turns of the metal band having free play with respect to each other.9. A pipe according to claim 8, wherein the flat metal band is cementedto said outer envelope substantially at a level of an edge of the metalband in contact with said outer envelope.
 10. A pipe according to claim8, wherein a layer of grease is only substantially interposed betweensaid outer envelope and said at least one layer of a flexible, thin andflat metal band.
 11. A pipe according to claim 1, wherein the flexible,thin and flat metal band has a composition containing chromium and atleast one metal selected from the group consisting of cobalt, nickel andmolybdenum.
 12. A pipe according to claim 1, wherein a layer of greaseis only substantially interposed between said inner sheath and said atleast one layer of a flexible, thin and flat metal band.
 13. A pipeaccording to claim 1, wherein a layer of grease is interposed betweenturns of the at least one layer of a flexible, thin and flat metal bandin the overlapping zones.
 14. A pipe according to claim 1, wherein saidmetal layer comprises at least two overlapping layers of flexible, thinand flat metal bands, a layer of one flexible, thin and flat metal bandbeing in contact with the inner sheath and being cemented thereto over apart of the width of the one flexible, thin and flat metal band, and alayer of another flexible, thin and metal band being in contact with theouter envelope and being cemented thereto over a part of the width ofthe another flexible, thin and flat metal band; said two layers of theflexible, thin and flat metal bands having free play with respect toeach other.
 15. A pipe according to claim 1, wherein said outer envelopecomprises a composite material containing a reinforcing fiber stripimpregnated with a resin, and the at least one metal layer of aflexible, thin and flat metal band is cemented to said inner flexiblesheath over at least the majority of the width of the metal band.
 16. Apipe according to claim 15, further comprising a flexible sheath ofpolymeric material extruded over said metal layer of the flexible, thinand flat metal band and arranged beneath said outer envelope.
 17. A pipeaccording to claim 15, wherein said metal layer comprises a layer of aflexible, thin and flat metal band adhering to the outer envelope overat least a part of the width of the metal layer in contact with saidouter envelope.
 18. A pipe according to claim 1, wherein said at leastone layer of a flexible, thin and flat metal band wound spirally at saidwinding angle is cemented to said inner sheath or to the outer envelopeover a width of said metal band in contact with said inner sheath orwith said outer envelope that varies from a width of an overlapping zoneto at least a major part of a width in contact with the inner sheath orthe outer envelope.
 19. A pipe according to claim 1, wherein said atleast one layer of a flexible, thin and flat metal band comprises aflexible, thin and flat metal band having a width of at least 1 cm and athickness of from 1/100 mm to 5/10 mm.